Thermochemistry and structure of atoms

Abstract

1. The heat of hydrolysis of gaseous boron chloride has been determined. 2. Applying the concepts of electronegativity, of degree of ionicity of bonds, and of the function (see our previous communication) it has been shown that inversion cannot take place in the heats of formation of the series of chlorides B, Al, Se, Y, and La, but that the rule of thermochemical logarithmics should be observed here. This allows of the derivation of the following values for heat of formation of BCl3 (keaI per male). $$B_{(cryst.)} + {3 \mathord{\left/ {\vphantom {3 2}} \right. \kern-\nulldelimiterspace} 2}Cl_{2_{(gas)} } = BCl_{3_{(cryst.)} } ,\Delta \underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle-}$}}{H} _{2S3} = - 114 \pm 3$$ or $$B_{(cryst.)} + {3 \mathord{\left/ {\vphantom {3 2}} \right. \kern-\nulldelimiterspace} 2}Cl_{2_{(gas)} } = BCl_{2_{(gaseous)} } ,\Delta \underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle-}$}}{H} _{2S3} = - 108 \pm 3.$$ 3. The experimental values found for the heat of hydrolysis of BCl3 show that the correct for its best of formation is in accordance with the expression $$2B_{(cryst.)} + {3 \mathord{\left/ {\vphantom {3 2}} \right. \kern-\nulldelimiterspace} 2}O_{2_{(gas)} } = B_2 O_{3_{(cryst.)} } ,\Delta \underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle-}$}}{H} _{2S3} = - 341 \pm 3.$$ This confirms the work of Reth and Todd and Miller, but not Eggersgluess, Monroe, and Parker, and also shows that the results calculated indirectly by Johnston, Hersch, and Kerr for the heat of formation of B2O3 are wrong. 4. Combining the measurements of specific heat (entropy) give by these authors with the results presented in the present paper, the following figure can be derived for the free energy of formation of boron oxide (keal per moles $$2B_{(cryst.)} + {3 \mathord{\left/ {\vphantom {3 2}} \right. \kern-\nulldelimiterspace} 2}O_{2_{(gas)} } = B_2 O_{3_{(cryst.)} } ,\Delta \underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle-}$}}{F} _{2S3} = - 322 \pm 3$$ 5. The rule of thermochemical logarithmics is followed without exception by the chlorides and oxides of the elements of Group III of the periodic system.